As battery filler/vent caps were found dislodged, it would suggest that chemical reaction in the battery was intense/violent confirming that the battery was being overcharged by a fault in the alternator. The intense chemical reaction would generate extensive heat, resulting in the release of hydrogen into the engine-room and causing the acid from the battery to overflow. The presence of sulphuric acid between the terminals could create a short at the battery terminals with consequential arcing. It was not possible to reconstruct the precise condition of the engine-room at the time the fire started because the site was disturbed before the vessel arrived in port, both during and after the fire-fighting. However, the engine-room of a typical fishing vessel, such as the NORTHERNVENTURE, would likely contain some oily residues. The wooden structure of the engine-room had most likely absorbed these residues in such quantities as to sustain a fire. If these conditions were present, arcing at the battery terminals in the proximity of combustible materials and hydrogen likely initiated the fire. The prompt and effective action by the crew in dealing with the emergency situation and successfully extinguishing the fire can be attributed to the MED training that some of them had received.Analysis As battery filler/vent caps were found dislodged, it would suggest that chemical reaction in the battery was intense/violent confirming that the battery was being overcharged by a fault in the alternator. The intense chemical reaction would generate extensive heat, resulting in the release of hydrogen into the engine-room and causing the acid from the battery to overflow. The presence of sulphuric acid between the terminals could create a short at the battery terminals with consequential arcing. It was not possible to reconstruct the precise condition of the engine-room at the time the fire started because the site was disturbed before the vessel arrived in port, both during and after the fire-fighting. However, the engine-room of a typical fishing vessel, such as the NORTHERNVENTURE, would likely contain some oily residues. The wooden structure of the engine-room had most likely absorbed these residues in such quantities as to sustain a fire. If these conditions were present, arcing at the battery terminals in the proximity of combustible materials and hydrogen likely initiated the fire. The prompt and effective action by the crew in dealing with the emergency situation and successfully extinguishing the fire can be attributed to the MED training that some of them had received. Equipment Maintenance and Inspection Although the Halon 1211 automatic fire-extinguishing system was fitted with a pressure gauge to indicate the quantity of charge in the cylinder, no examination was carried out by the skipper. As the equipment is required to be used in an emergency and as the fitting of such equipment could provide a false sense of security, it is imperative that the equipment be maintained in proper working order. Failure to do so has the potential to compromise safety. Although it was reported that the Halon automatic fire-extinguishing system had been inspected by TC Marine, there is no record of it on SIRS II (Ship Inspection Reporting System). As there is no detail of the inspection record, it cannot be determined what criteria, if any, were used by the attending surveyor to ensure that the equipment was in proper working order. Barring the actual temperature measurement, there is no other criterion established by TC Marine for use by attending surveyors to assist in determining that the temperature setting on the equipment is appropriate. Selection of Temperature Settings for Automatic Fire-extinguishing Systems Timely activation of the automatic fire-extinguishing system is essential to effectively control and successfully extinguish a fire. Hence, an unduly high temperature setting of the sprinkler head would allow the fire to progress and spread undetected for a period of time. Delayed detection of a fire has the potential to cause extensive damage and jeopardize the safety of the vessel and her crew. Because the automatic fire-extinguishing system is intended to activate in sufficient time to prevent a fire from spreading in a compartment, the temperature rating selection for this type of equipment should be matched to the anticipated hazards being targeted and to the maximum deck-head temperature expected in the enclosure being protected. In order to provide a margin of safety to prevent premature operation of the system (baring the presence of any unique circumstances), the temperature rating of a sprinkler system is typically selected to be approximately 22C to 45C above the maximum ceiling temperature of the room being protected(3). In this instance, the maximum deck-head temperature expected in the engine-room was 45C during summer operations, whereas the sprinkler head in use was temperature-rated for 141C. Hence, it is important that a proper compromise be struck when selecting the temperature rating of an extinguisher sensor to ensure that the margin of safety chosen to prevent premature activation does not jeopardize the quick operation of the system to control a fire and to prevent its spread. The automatic fire-extinguishing system did not activate because the fire did not generate enough heat over a long enough period of time at the position of the sprinkler head. The sprinkler head in use was temperature-rated for 141C which is a high temperature classification for use in the engine-room of this vessel. When tested following the occurrence, the automatic fire-extinguishing system in the engine-room performed as designed. The depleted condition of the fire-extinguishing system was attributable to a slow, low-volume leak in the Schrader valve. The leak in the Schrader valve was caused by a cracked and deteriorated valve core plunger seat washer. Lack of servicing and routine inspection permitted the depleted condition of the fire-extinguishing system to remain undetected for a period of time. The automatic fire-extinguishing system did not activate because the fire did not generate enough heat over a long enough period of time at the position of the sprinkler head. The sprinkler head in use was temperature-rated for 141C which is a high temperature classification for use in the engine-room of this vessel. When tested following the occurrence, the automatic fire-extinguishing system in the engine-room performed as designed. The depleted condition of the fire-extinguishing system was attributable to a slow, low-volume leak in the Schrader valve. The leak in the Schrader valve was caused by a cracked and deteriorated valve core plunger seat washer. Lack of servicing and routine inspection permitted the depleted condition of the fire-extinguishing system to remain undetected for a period of time.Findings The automatic fire-extinguishing system did not activate because the fire did not generate enough heat over a long enough period of time at the position of the sprinkler head. The sprinkler head in use was temperature-rated for 141C which is a high temperature classification for use in the engine-room of this vessel. When tested following the occurrence, the automatic fire-extinguishing system in the engine-room performed as designed. The depleted condition of the fire-extinguishing system was attributable to a slow, low-volume leak in the Schrader valve. The leak in the Schrader valve was caused by a cracked and deteriorated valve core plunger seat washer. Lack of servicing and routine inspection permitted the depleted condition of the fire-extinguishing system to remain undetected for a period of time. The automatic fire-extinguishing system did not activate because the fire did not generate enough heat over a long enough period of time at the position of the sprinkler head. The sprinkler head in use was temperature-rated for 141C which is a high temperature classification for use in the engine-room of this vessel. When tested following the occurrence, the automatic fire-extinguishing system in the engine-room performed as designed. The depleted condition of the fire-extinguishing system was attributable to a slow, low-volume leak in the Schrader valve. The leak in the Schrader valve was caused by a cracked and deteriorated valve core plunger seat washer. Lack of servicing and routine inspection permitted the depleted condition of the fire-extinguishing system to remain undetected for a period of time. A fire broke out in the engine-room of the NORTHERNVENTURE most probably because arcing at the battery terminals ignited combustible materials. A contributing factor to the occurrence was the malfunction of the alternator which allowed the battery to be overcharged.Causes and Contributing Factors A fire broke out in the engine-room of the NORTHERNVENTURE most probably because arcing at the battery terminals ignited combustible materials. A contributing factor to the occurrence was the malfunction of the alternator which allowed the battery to be overcharged. In April 1996, TSB Marine Safety Advisory No. 04/96 was forwarded to Transport Canada (TC) concerning the installation of automatic fire-extinguishing systems with improper activation temperature ratings. As a result, TC Marine issued Ship Safety Bulletin No. 08/96 (dated 03 July 1996) to advise the industry that activation temperature settings for automatic smothering systems on vessels should be no higher than 30C (86F) above the highest ambient temperature in the location of the actuator. TC also indicated that a requirement for a minimum/maximum activation temperature will be considered in the proposed Fire Detection and Extinguishing Equipment Regulations (CSA-20).Safety Action Taken In April 1996, TSB Marine Safety Advisory No. 04/96 was forwarded to Transport Canada (TC) concerning the installation of automatic fire-extinguishing systems with improper activation temperature ratings. As a result, TC Marine issued Ship Safety Bulletin No. 08/96 (dated 03 July 1996) to advise the industry that activation temperature settings for automatic smothering systems on vessels should be no higher than 30C (86F) above the highest ambient temperature in the location of the actuator. TC also indicated that a requirement for a minimum/maximum activation temperature will be considered in the proposed Fire Detection and Extinguishing Equipment Regulations (CSA-20).